Large area, low capacitance, GaAs nanowire photodetector with a transparent Schottky collecting junction

Abstract

We present experimental results on a GaAs/Indium-Tin-Oxide Schottky-like heterojunction photodetector based on a nanowire device geometry. By distributing the active detecting area over an array of nanowires, it is possible to achieve large area detection with low capacitance. Devices with bare GaAs and passivated AlGaAs/GaAs nanowires are fabricated to compare the responsivity with and without surface passivation. We are able to achieve responsivity of >0.5A/W and Signal-Noise-Ratio in excess of 7 dB for 2 V applied reverse bias with passivated nanowire devices. Capacitance-voltage measurement yields <5 nF/cm2, which shows a strong possibility for high-speed applications with a broad area device.

Efficient Schottky-like junction GaAs nanowire photodetector with 9 GHz modulation bandwidth with large active area

“…8 This phenomenon has also been reported to manifest itself in the dynamic properties of planar photodiodes via the reduction of average carrier velocity. 9 To first confirm device quality, the responsivity of the studied devices was measured and found to match the results seen previously.…”

“…6,7 Devices based on an array of contacted nanowires have experimentally demonstrated capacitance of 5 nF/cm 2 and responsivity of 0.65 A/W. 8 In this Letter, these characteristics are exploited to fabricate efficient, large-area detectors with modulation bandwidth in the range of several gigahertz.…”

“…9 To first confirm device quality, the responsivity of the studied devices was measured and found to match the results seen previously. 8 In order to accurately measure modulation bandwidth as a means to observe material characteristics, circuit parasitics must be de-embedded. To quantify the maximum modulation frequency due to parasitics, reflection impedance, S 22 , measurements at 0 V applied bias with no optical excitation were carried out.…”

“…8 1 mm square arrays of 220 nm diameter nanowires were grown $1.2 lm tall with 600 nm pitch and infiltrated with hydrogen silsesquioxane (Dow-Corning, XR-1541-002). The upper region of the nanowires were contacted by Indium-Tin-Oxide (ITO) that was sputtered on at 200 W (Ulvac JSP-8000) which easily allows for lift-off.…”

Evolution of GaAs nanowire geometry in selective area epitaxy

“…Semiconductor nanowires (NWs) grown by the selective area epitaxy (SAE) technique have recently been shown to be promising for various photonic and electronic device applications. 1 Many SAE-NW-based devices have recently been demonstrated including photonic crystal cavities, 2 Fabry-Perot resonators, 3 lasers, 4 photo-detectors, 5,6 and various solar cell designs. [7][8][9] In addition, research demonstrating the direct growth of compound semiconductor SAE-NWs on silicon has shown a pathway to direct integration of photonic devices onto CMOS chips, possibly providing a much sought after solution to a long standing technical challenge.…”